Just to make it easy for you-check the nm on the vial of the primer. Suppose to find 27.4 nm or so. Multiply by 10 and will be  274 uL. This is 100uM Stock.

In an eppendorf tube add 80 uL H2O and then 10 uL from the diluted forward and backward primers then you will have 10uL working solution.

Do not forget to mixed and spin each time.

Good luck!

thank you very much Dr Zakaria for your Answer I found a number was written on the tube cover

a longer way of doing it will be to take the amount they sent, calculate the molecular weight of the primer and then Use molarity formula for calculating the volume required to make 100 micro molar stock. 

Thank you Dr Chanakya but nothing is written on the tube except the gene sequence how to calculate the molecular weight 

Hi Mohamed,

1. You should ask the company for the data sheet of the primer you ordered. The molecular weight (M.W.), nmole of your primers and primer DNA sequences are all basic information they should provide. These info should be listed on the info sheet and send to the users.

2. When you found out how much nmole you have for your primers (as you said you have found it in your earlier post), you should be able to prepare a 100 uM primer stock. See point #5 of this link:  http://www.le.ac.uk/bl/phh4/oligos.htm

Thank you very much Dr Yuan i find a number was written on the tube caps and i do not if it was the nmole or not

Hi Mohamed,

You have to find out. Without these info, you cannot make a proper primer concentration. The number on the lid may not be the nmole number, but instead a company's product 'batch' number.

Check your lab members to see if anyone received the package and filed away the info sheet (usually the lab manager will do so). I haven't seen that a purchased primer comes with only a tube and an unknow number on the top.